Optimization method for the determination of material parameters in damaged composite structures

An optimization method to identify the material parameters of composite structures using an inverse method is proposed. This methodology compares experimental results with their numerical reproduction using the finite element method in order to obtain an estimation of the error between the results. This error estimation is then used by an evolutionary optimizer to determine, in an iterative process, the value of the material parameters which result in the best numerical fit. The novelty of the method is in the coupling between the simple genetic algorithm and the mixing theory used to numerically reproduce the composite behavior. The methodology proposed has been validated through a simple example which illustrates the exploitability of the method in relation to the modeling of damaged composite structures.Peer ReviewedPostprint (author’s final draft

Constraining a bulk viscous matter-dominated cosmological model using SNe Ia, CMB and LSS

We present and constrain a cosmological model which component is a pressureless fluid with bulk viscosity as an explanation for the present accelerated expansion of the universe. We study the particular model of a constant bulk viscosity coefficient \zeta_m. The possible values of \zeta_m are constrained using the cosmological tests of SNe Ia Gold 2006 sample, the CMB shift parameter R from the three-year WMAP observations, the Baryon Acoustic Oscillation (BAO) peak A from the Sloan Digital Sky Survey (SDSS) and the Second Law of Thermodynamics (SLT). It was found that this model is in agreement with the SLT using only the SNe Ia test. However when the model is submitted to the three cosmological tests together (SNe+CMB+BAO) the results are: 1.- the model violates the SLT, 2.- predicts a value of H_0 \approx 53 km sec^{-1} Mpc^{-1} for the Hubble constant, and 3.- we obtain a bad fit to data with a \chi^2_{min} \approx 400 (\chi^2_{d.o.f.} \approx 2.2). These results indicate that this model is ruled out by the observations.Comment: 4 pages, 1 figure. Work presented in the XI Mexican Workshop on Particles and Fields, Tuxtla Gutierrez, Mexico, nov 7-12, 2007. Submitted to AIP Conference Proceedings of this conferenc

Effect of degree correlations above the first shell on the percolation transition

The use of degree-degree correlations to model realistic networks which are characterized by their Pearson's coefficient, has become widespread. However the effect on how different correlation algorithms produce different results on processes on top of them, has not yet been discussed. In this letter, using different correlation algorithms to generate assortative networks, we show that for very assortative networks the behavior of the main observables in percolation processes depends on the algorithm used to build the network. The different alghoritms used here introduce different inner structures that are missed in Pearson's coefficient. We explain the different behaviors through a generalization of Pearson's coefficient that allows to study the correlations at chemical distances l from a root node. We apply our findings to real networks.Comment: In press EP

The Effect Of Problem Based Learning On Undergraduate Oral Communication Competency

Purpose:  The aim of this study was to ascertain the effect of Problem Based Learning (PBL) on student oral communication competency gains. Methods:  Eighty students from two consecutive undergraduate Kinesiology courses (Spring semesters, 2014-15) formed into 29 small groups and were studied.  Oral communication competency was assessed using a customized rubric and digital recordings of student presentations.  Changes to oral communication competency across time were tested using a dependent t-test; a < .05. Results:  Significant inter-rater agreement was found at both time points for oral communication rating, and student groups demonstrated significant oral communication gains across time.  Conclusions:  Collaborative learning was shown to improve students’ oral communication competency. Future study is required to determine the influence of student motivation and goal orientation on oral communication competency, in relation to the various phases of knowledge creation occurring within student groups.

Health Care Human Factors/Ergonomics Fieldwork in Home and Community Settings

Designing innovations aligned with patients’ needs and workflows requires human factors/ergonomics (HF/E) fieldwork in home and community settings. Fieldwork in these extra-institutional settings is challenged by a need to balance the occasionally competing priorities of patient and informal caregiver participants, study team members, and the overall project. We offer several strategies that HF/E professionals can use before, during, and after home and community site visits to optimize fieldwork and mitigate challenges in these settings. Strategies include interacting respectfully with participants, documenting the visit, managing the study team–participant relationship, and engaging in dialogue with institutional review boards

Finite-Size-Scaling at the Jamming Transition: Corrections to Scaling and the Correlation Length Critical Exponent

We carry out a finite size scaling analysis of the jamming transition in frictionless bi-disperse soft core disks in two dimensions. We consider two different jamming protocols: (i) quench from random initial positions, and (ii) quasistatic shearing. By considering the fraction of jammed states as a function of packing fraction for systems with different numbers of particles, we determine the spatial correlation length critical exponent $\nu\approx 1$, and show that corrections to scaling are crucial for analyzing the data. We show that earlier numerical results yielding $\nu<1$ are due to the improper neglect of these corrections.Comment: 5 pages, 4 figures -- slightly revised version as accepted for Phys. Rev. E Rapid Communication